1. Field of the Invention
The present invention relates to a sealless pump which does not employ mechanical seals (seal members) but adopts non-contact type bearings for bearings of a motor.
2. Description of the Prior Art
For example, a sealless pump utilizes an impeller being rotated by a motor so as to discharge fluid and the like. Normally, mechanical seals and the like are used in order to separate a pump portion and a motor portion.
However, it is difficult to completely prevent fluid and the like of very low temperature and very high temperature or fluid and the like of very low pressure and very high pressure from leaking, by using mechanical seals. Therefore, a sealless pump employing no mechanical seals has been developed.
As a sealless pump, there is such one as integrates a motor and a pump and is sealed in a container (a can and the like) (for example, a canned motor pump). Because such a sealless pump as mentioned above is completely sealed, fluid and the like of very low temperature and very high temperature or chemicals and the like of strong acid, strong alkali and the like do not absolutely leak.
However, even the bearings of a rotating shaft will be soaked in fluid and the like. Additionally, a bearing member is sometimes worn away and worn particles serve as dusts, which result in contamination of liquid. Therefore, a sealless pump adopting non-contact type bearings has been developed.
For example, a sealless pump 189 in a patent literature 1 (Publication Bulletin of Patent Application Laid Open 9-264292 (Laid-Open Disclosure Date: Oct. 7, 1997) shown in FIG. 11 is such a sealless pump as has a non-contact type magnetic bearing 191 provided to one end of a rotating shaft 122 and has a non-contact type hydrostatic bearing 192 provided to the other end of the rotating shaft 122.
This sealless pump 189 has a magnetic bearing (magnetic bearing equipment), which conventionally has been installed to both ends of the rotating shaft, provided to one end only, thereby achieving size down of an entire sealless pump as well as cost reduction.
And now, in such a sealless pump as described hereinabove, the temperature of liquid being pumped which can be pneumatically transmitted is limited by the predetermined heat resistance insulation temperature of the motor. (See FIG. 12, a partial excerpt from JIS C 4003-198.)
Then, in the sealless pump 189 as described in the patent literature 1, when the temperature of fluid and the like which are pneumatically transmitted becomes high, the heat resistance insulation temperature of the motor (a rotor, a stator and the like) must be enhanced, too. Otherwise, an entrance port 193 must be installed in order to flow fluid for cooling fluid as illustrated.
And then, when fluid and the like of very high temperature and the like are pneumatically transmitted by such a sealless pump 189 as shown in the patent literature 1, cost will be necessary for enhancing the heat resistance insulation temperature of the motor. In other words, a problem will occur which will lead to a rising cost of the sealless pump itself.
Additionally, when an entrance port 193 for cooling is provided and cooling fluid is flowed through the entrance port 193, the cooling fluid will be introduced to a suction port 115 of the sealless pump 189 by way of an inside passageway 194 which is provided to a manifold casing 117 of the pump.
Then, when the cooling fluid is introduced and mixed in, small babbles and dusts and the like (particles and the like) will be generated. In the result, a problem will occur that particles get mixed in the fluid and the like being sent forth from a discharge port 116 of the sealless pump 189.